Disclosed are methods for codebook sub-sampling. In various implementations, a wireless terminal receives a reference signal, determines, based on the reference signal, a first precoding index i2 for a first subband and a second precoding index i'2 for a second subband. The wireless terminal transmits a representation of i2 and a representation of i'2 to a base station. In various implementations, i'2 belongs to the set Si2 which, in one implementation, equals {mod(i2 -K1+k,K), k=0,1,...,K2}, where K1>1, and where K2>1 and K>1 are integers. According to an implementation, the wireless terminal receives the reference signal from a first base station and transmits the representations of i2 and i'2 to a second base station.